You want to use SQL? You can use the itemlist class and a Iterator...
But, if you want to make raw queries, turn on the debug and you will see the queries in the footer!

Thanks for your reply, Walter.

If you would please, can you provide an example on how to use that class - say, to create a result set of posts (items) and the blog each belongs to?

Thanks.

You can open a skin and see the methods in action.. A sample:

		while( $Item = & mainlist_get_item() )
		{
                  // now you will have a Item, a blog posts, with a lot of methods:
                  $Item->title();
		// Display CONTENT:
		$Item->content_teaser( array(
				'before'      => '',
				'after'       => '',
			) );
		$Item->more_link( array(
				'before'    => $params['before_more_link'],
				'after'     => $params['after_more_link'],
				'link_text' => $params['more_link_text'],
			) );
		$Item->content_extension( array(
				'before'      => '',
				'after'       => '',
			) );

		// Links to post pages (for multipage posts):
		$Item->page_links( '<p class="right">'.T_('Pages:').' ', '</p>', ' &middot; ' );
                  }

Open some skin, open _item_content.inc.php and enjoy! You can use the online docs, on http://docs.b2evolution.net

Thanks for the info, Walter.

I'll give it a try.